Silica Gel Research Articles

Analytical Assessment of the Quality of Dietary Supplements and Cosmetic Products Containing Xanthohumol by Thin-Layer Chromatography Along with the Estimation of Its Antioxidant Potential

Xanthohumol, a prenylated chalcone in the flavonoid group, naturally occurs in many plants and exhibits antioxidant, anticancer, anti-inflammatory, antibacterial, and antiviral effects. The growing interest in xanthohumol due to its potential therapeutic properties has led to the increase in the pool of products available on the market. The novelty of this study is the proposal of a rapid and cost-effective procedure useful for performing quality control on products containing xanthohumol in the form of dietary supplements and cosmetics as well as testing their stability. For this purpose, the thin-layer chromatography method with densitometric detection was used, which was validated in accordance with ICH (International Conference on Harmonization) guidelines. The mobile phase was toluene, 1,4-dioxane, and glacial acetic acid (37:10:1.5 v/v/v), and TLC silica gel 60 F254 plates were used as the stationary phase. The validation process assessed linearity, with a correlation coefficient (r) of 0.9987. The calculated LOD (limit of detection) and LOQ (limit of quantification) values were 3.82 and 11.57 ng/spot, respectively. Accuracy was evaluated by determining percentage recovery at three concentration levels (80, 100, and 120%), with an average recovery of 100% and RSD below 1%, confirming good accuracy. Precision was indicated by an RSD of less than 2.20%. The average content of xanthohumol in dietary supplements ranged from about 8 to 29% of the content declared by the manufacturers. The stability tests showed that XN decomposes most slowly in water (t0.5 = 10.86 h) compared with acidic (t0.5 = 10.80 h) and alkaline solutions (t0.5 = 7.39 h), as well as in the presence of an oxidizing agent (t0.5 = 18.38 h), at all tested temperatures, which is confirmed by the calculated kinetic parameters. In the tests of antioxidant capacity, xanthohumol shows significantly higher radical scavenging capacity than vitamin C in the entire range of analyzed concentrations (0.03–2.40 mmol/L).

Immobilized Horseradish Peroxidase on Enriched Diazo-Activated Silica Gel Harnessed High Biocatalytic Performance at a Steady State in Organic Solvent.

Dimethyldichlorosilane (DMDCS), an efficient silane coupling reagent appearing between the -OH groups of silica gel (SG) and picric acid, instantaneously produces a derivative enriched with nitro groups. The nitro group acting as an end-cap terminates the reaction and subsequently was converted into diazo to couple tyrosine's phenol ring via its O-carbon, the inert center to immobilize horseradish peroxidase (HRP) in a multipoint mode. It maintains the status quo of the native enzyme's protein folding and the entire protein groups' chemistry. The molecular formula of the synthesized material was verified and appeared as {Si(OSi)4 (H2O)x}n{-O-Si(CH3)2-O-C6H2(N+≡N)3(HRP)}4·yH2O; the parameters were evaluated as x = 0.5, n = 1158, and y = 752. The immobilized biocatalyst's activity in organic solvents was 1.5 times better than that in an aqueous medium; it worked smoothly, wherein the activity in both solvents stabilized at six months and continued up to nine months at 63 ± 3% compared to the initial.

Efficient Selective CO2 Composite Sorbent from Amino Acid Ionic Liquids and Silica Gel: 2H NMR Spectroscopy Provides Insight on the CO2-Binding Mechanism and in-Pore Microscopic Viscosity.

A promising CO2 sorbent based on the [Emim][Gly] (1-ethyl-3-methylimidazolium glycinate)/silica gel composite has been studied. CO2 sorption experiments have shown that the optimum loading of [Emim][Gly] ionic liquid in silica gel is 40 wt.%. The 2-step process CO2 binding mechanism in [Emim][Gly] has been proposed based on the results of sorption experiments, 2H NMR spectroscopy and ab-initio calculations. The impact of CO2 on the microscopic viscosity and the dynamical melting of ionic liquid has been thoroughly investigated. 2H NMR spectroscopy has revealed that CO2 strongly binds cation and anion in [Emim][Gly], forcing them to move in a correlated fashion.

Recovery of Titanium from Red Mud Using Carbothermic Reduction and High Pressure Leaching of the Slag in an Autoclave

Red mud is a by-product of alumina production, which is largely stored in landfills that can endanger the environment. Red mud, or bauxite residue, is a mixture of inorganic compounds of iron, aluminum, sodium, titanium, calcium and silicon mostly, as well as a large number of rare earth elements in small quantities. Although certain methods of using red mud already exist, none of them have been widely implemented on a large scale. This paper proposes a combination of two methods for the utilization of red mud, first by carbothermic reduction and then, by leaching under high pressure in an autoclave in order to extract useful components from it with a focus on titanium. In the first part of the work, the red mud was reduced with carbon at 1600 °C in an electric arc furnace, with the aim of removing as much iron as possible using magnetic separation. After separation, the slag is leached in an autoclave at different parameters in order to obtain the highest possible yield of titanium, aiming for the formation of titanium oxysulfate and avoiding silica gel formation. A maximal leaching efficiency of titanium of 95% was reached at 150 °C using 5 mol/L sulfuric acid with 9 bar oxygen in 2 h. We found that high-pressure conditions enabled avoiding the formation of silica gel during leaching of the slag using 5 mol/L sulfuric acid, which is a big problem at atmospheric pressure. Previously silica gel formation was prevented using the dry digestion process with 12 mol/L sulfuric acid under atmospheric pressure.

Bacillus xiamenensis Inhibits the Growth of Moraxella osloensis by Producing Indole-3-Carboxaldehyde.

Moraxella osloensis, a gram-negative rod-shaped bacterium found on human skin, produces 4-methyl-3-hexenoic acid, contributing to clothing and body malodor. M. osloensis is resistant to UV light, drying, and antimicrobials, making its eradication challenging. As the skin is low in nutrients, commensal bacteria compete for resources and use diverse strategies to inhibit their competitors. Therefore, skin-derived bacteria that exhibited growth-inhibitory activity against M. osloensis were searched. Screening skin-derived bacteria using a coculture halo assay revealed that Bacillus xiamenensis formed an inhibition zone with M. osloensis. Coculture plates were extracted with ethyl acetate and fractionated using a silica gel column and preparative thin-layer chromatography to isolate the active compound from the B. xiamenensis metabolites. Nuclear magnetic resonance spectroscopy identified the active compound as indole-3-carboxaldehyde, which has low toxicity in humans. At soluble concentrations, indole-3-carboxaldehyde does not inhibit the growth of other bacteria, such as Staphylococcus aureus, Escherichia coli, and Bacillus subtilis, suggesting M. osloensis is highly sensitive to indole-3-carboxaldehyde. These findings highlight B. xiamenensis as a promising candidate for the development of a skin probiotic to promote skin health and combat malodor-causing bacteria.

Improving the Wetting Properties of PDMS/PVA-PEG Hydrophilic Sponges through the Addition of Wetting Agents

The optimization stage of the PDMS/PVA-PEG hydrophilic sponge has been prepared to increase water absorption, through the addition of wetting agents including bentonite, silicon oil, silica gel, and sodium hydrogen carbonate. The bentonite is purified by magnetic separation with a montmorillonite (MMT) content of approximately 33,17%. Silicon oil has hydrophilic properties due to the high surface energy of silicon dioxide, while silica gel is an adsorbent that will produce high silanol groups, and NaHCO3 is used to expand pores when releasing CO2. PDMS/PVA-PEG hydrophilic sponges were prepared with various ratios (w/w) PDMS: silicone oil: silica gel: NaHCO3: ZnCl2: PVA: PEG= 1:2:2:2,5:5:5:10 (V1 sponge); 1:2:2:1.25:5:5:10 (V2 sponge); 1:2:2:0:5:5:10 (V3 sponge). The sponge synthesis process is conducted by heating at a temperature of 110°C for 4 hours. The hydrophilic sponge composite incorporated bentonite in a ratio of 1:1 (w/w) to obtain VB1 sponge, VB2 sponge, and VB3 sponge have contact angle values 37.0°, 56.6°, and 58.8°, respectively. NaHCO3 can increase the pore of the sponge, therefore the condition can increase the hydrophilicity. The contact angle of V1 sponge is 45.2°, while VB1 is 37°.0°, which indicates that bentonite can enhance hydrophilic properties. Excellent wetting properties will imply good dewatering properties for hydrocarbon fuel refining.

Ester-Modified Sodium Silicate Grout Material for Moraine Stabilization: Synthesis and Freeze-Thaw Resistance

To achieve effective consolidation of fine particles in moraine and enhance the freeze-thaw resistance of the consolidated body, this study developed a novel grouting material using sodium silicate, lipid-based curing agents, and acidic catalysts. The gelation time and rheological properties of this material were tested. The freeze-thaw resistance was studied through changes in uniaxial compressive strength (UCS) after freeze-thaw cycles, while the consolidation mechanism was analyzed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The experimental results indicate that the material’s gelation time can be controlled between 30s and 1600s, with an initial viscosity ranging from 5.9 to 9.8 mPa·s. Predictive models for these two indicators were established, and variance analysis revealed the influence ranking for gelation time: phosphoric acid dosage had the greatest effect, followed by EGDA content, with the Baume degree of sodium silicate having the least effect. The initial viscosity positively correlated with the Baume degree of sodium silicate and exhibited exponential growth over time. EGDA addition enhanced UCS by over 450%, reaching 1.2 MPa. During freeze-thaw cycles, strength degradation of the consolidated body was reduced by 10% to 30%. Microstructural tests showed that EGDA promotes silica gel formation and creates a network structure with unreacted sodium silicate, forming a dense consolidated body with moraine fine particles, thereby enhancing freeze-thaw resistance. These findings provide design references and theoretical support for moraine grouting in cold regions.

Characteristics of carbazole compounds in ultra-deep marine oil from Fuman oilfield, Tarim Basin: Significance for thermal maturity assessment of crude oil

Carbazoles in Ordovician ultra-deep marine oil from the FI17 fault zone in Fuman oilfield (Tarim Basin) were separated using a recently proposed silica gel column chromatographic method and the enriched fractions were analyzed by GC–MS. Biomarker and carbon isotope signatures revealed that all oil in the study area was produced from the same source rock and that compositional differences can be attributed to thermal maturation. The convergent ratios of N-H shielded isomers/N-H half shielded isomers and benzo[a]carbazole/(benzo[a]carbazole + benzo[c]carbazole) suggested that carbazoles in crude oil had not been affected by vertical migration. Therefore, thermal maturity was identified as the main controlling factor affecting chages of carbazole concentrations and ratios in crude oil. The concentrations of the total carbazole and its three isomers (N-H shielded isomers, N-H half shielded isomers and exposed isomers) in crude oil decreased sharply with increasing maturity. The 1,8-dimethylcarbazole/carbazole (1,8-MCa/Ca) and 1,8-dimethylcarbazole/2,4-dimethylcarbazole (1,8-MCa/2,4-MCa) ratios showed significant correlation with maturity expressed as %VRE (the vitrinite reflectance equivalent converted from MPI1 and MPR) when %VRE is <1.2 %. Similar trends were observed in the 1-methylcarbazole/3-methylcarbazole (1-MCa/3-MCa) as well as 1,8-dimethylcarbazole/2,6- dimethylcarbazole (1,8-DMCa/2,6-DMCa), (1,5- dimethylcarbazole + 3-ethylcarbazole)/2, 6-dimethylcarbazole ((1, 5-DMCa + 3-ECa)/2, 6-DMCa), and (1, 4-dimethylcarbazole + 4-ethylcarbazole)/2, 6-dimethylcarbazole ((1, 4-DMCa + 4-ECa)/2, 6-DMCa) when the %VRE of crude oil exceeds 1.0 %. This indicated that the concentrations and ratios of carbazole can be used to qualitatively evaluate crude oil maturity. The ratio of 1,8-dimethylcarbazole/1-ethylcarbazole (1,8-DMCa/1-ECa) showed a strict linear relationship with %VRE. The maturity of marine oil can be calculated using the formulas %Rc (the vitrinite reflectance equivalent calculated from MPI1) = −0.0335(1, 8-DMCa/1-ECa) + 1.2902 or %Rc1 (the vitrinite reflectance equivalent calculated from MPR) = −0.0405 (1, 8-DMCa/1-ECa) + 1.3418. The study can be helpful for exploring ultra-deep hydrocarbons and restoring the thermal history of source rocks in the Tarim Basin.

Silica gels doped with gold nanoparticles and gold thiolate complexes: The effect of heating and preparation conditions

A novel sol-gel strategy for the preparation of silica nanocomposites, containing gold nanoparticles (AuNPs), Au(I)-thiolate complexes (Au-SC12) or both disperse phases is demonstrated. The color of the species depends on the size and surrounding of the AuNPs. The nanocomposites obtained are characterized with UV/Vis reflectance spectroscopy, X-Ray diffraction, TEM / EDAX and thermal conductivity measurements. An analysis of the UV/VIS spectra, based on Mie's theory, suggests the presence of 5 - 30 nm AuNPs with different chemical surroundings. Heating of the nanocomposites at 700 °C leads to red or violet colored SiO2:AuNPs powders. The thermal conductivity of the nanocomposites is about 0.05–0.07 W/m.K, depending on sintering and chemical composition. A discussion about the microstructure of the composites is also presented.

Advanced HPTLC Method Development for Silibinin Analysis in Nanoformulated Scaffolds: A Box-Behnken Approach.

Silibinin (silybin), a bioactive component derived from the seeds of milk thistle (Silybum marianum), is recognized for its diverse pharmacological properties, including antioxidant, anti-inflammatory, and hepatoprotective effects. Given its therapeutic significance, accurately quantifying silybin in various formulations is essential. High-performance thin-layer chromatography (HPTLC) is a powerful analytical technique frequently used for this purpose. In this study, an HPTLC method was validated according to the International Council for Harmonization (ICH) guidelines to determine the concentration of silybin. The design of experiments (DoE), specifically the Box-Behnken design, was employed to optimize and understand the influence of critical method variables. The HPTLC method validation was performed using silica gel F254 HPTLC plates. The variables investigated included the composition of the mobile phase (% v/v), saturation time (minutes), and temperature in degree Celsius (°C), with the Box-Behnken design for optimization. The mobile phase consisted of chloroform, acetone, and formic acid in a 7:2:1 (v/v) ratio. Both the formulated scaffold and standard drug were applied to the plates, which were then processed in a twin chamber. After development, the plates were scanned at 288 nm using the Camag TLC Scanner IV with Vision CATS software. The validated HPTLC method demonstrated a strong linear relationship within the silybin concentration range of 2-10 μg/mL. The limit of detection (LOD) and limit of quantification (LOQ) for silybin were determined to be 0.469 and 1.423 μg/mL, respectively. Recovery studies indicated that the method provided accurate quantification, with recovery rates ranging from 97.53% to 99.82%. These results confirm the method's high accuracy, outstanding linearity, and reliability for the quantification of silybin in formulations. The validated HPTLC method proved to be a reliable analytical tool for the quantification of silybin in various formulations, particularly those containing polymers. The method's strong linearity, precision, and accuracy align with the ICH guidelines, making it suitable for routine analysis in quality control laboratories. The use of the Box-Behnken design for method optimization highlights the importance of systematic experimentation in achieving robust analytical outcomes.

Understanding Separation of Oil-Water Emulsions by High Surface Area Polymer Gels Using Experimental and Simulation Techniques.

This work examines the functional dependence of the efficiency of separation of oil-water emulsions on surfactant adsorption abilities of high surface area polymer gels. The work also develops an understanding of the factors and steps that are involved in emulsion separation processes using polymer gels. The work considers four polymer gels offering different surface energy values, namely, syndiotactic polystyrene (sPS), polyimide (PI), polyurea (PUA), and silica. The data reveal that surfactant adsorption abilities directly control the emulsion separation performance. The gels of sPS and PI destabilize the emulsions due to significant surfactant adsorption. The surfactant-lean oil droplets are then absorbed in the pores of sPS and PI gels due to the preferential wettability of the oil phase. The PUA and silica gels are more hydrophilic and show a lower surfactant adsorption ability. These gels cannot effectively remove the surfactant molecules from the emulsions, leading to a poor emulsion separation performance. The study uses simulation data to understand the adsorption characteristics of two poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer surfactants. The simulation results are used for the interpretation of emulsion separation performance by the gels.

Stability of immobilized L-arginine deiminase from Penicillium chrysogenum and evaluation of its anticancer activity

The aim of the present work was to immobilize L-arginine deiminase on suitable supports such as chitosan, alginate, and silica gel to study its stability. Additionally, the study aims to investigate the anticancer effects of the free purified enzyme on hepatocellular carcinoma (Hep-G2) and breast cancer (MCF-7) cell lines. L-arginine deiminase (ADI: EC 3.5.3.6) was immobilized on chitosan, Ca-alginate, and silica gel, with immobilization efficiencies of 89.0%, 72.8%, and 66.5%, respectively. The optimal immobilization time for the highest efficiency was 4 h. Increasing the concentration of glutaraldehyde improved the immobilization efficiency of ADI on chitosan. The chitosan-immobilized ADI retained about 45% of its activity after 8 cycles. The optimal pH values were 6 for the free purified ADI and 7 for the chitosan-immobilized ADI. The optimal temperature increased from 40 °C for the free enzyme to 45 °C after immobilization. The activation energies for the free and chitosan-immobilized enzymes were 71.335 kJ/mol and 64.011 kJ/mol, respectively. The Km values for the free and chitosan-immobilized ADI were 0.76 mM and 0.77 mM, respectively, while the Vmax values were 80.0 U/mg protein for the free ADI and 71.4 U/mg protein for the chitosan-immobilized ADI. After 30 days of storage at 4 °C, the residual activities were 40% for the free purified ADI and 84% for the chitosan-immobilized ADI. At 25 °C, the residual activities were 10% for the free ADI and 75% for the chitosan-immobilized ADI. The chitosan-immobilized ADI exhibited significantly higher stability against proteases such as pepsin and trypsin compared to the free enzyme. The purified ADI also demonstrated enhanced potential anticancer effects and significant cytotoxicity against the Hep-G2 and MCF-7 tumor cell lines compared to doxorubicin. These findings suggest that purified ADI has potential as an anticancer agent, though further in-depth studies are required.

Gas adsorption and separation applications of MOF materials

Abstract. Low-carbon hydrocarbons (C1-C4) are really important raw materials used in making different kinds of big molecules and stuff in industries. Before, people mostly used super cold cooling and a method where stuff gets soaked up. But these ways need big machines and use a lot of energy. So, scientists are trying to make new ways to separate things that don't use as much energy. One great idea is using how different gases stick to things to separate them. This idea could be a brilliant way to replace the old methods. The most important part of this idea is making things that can stick to the gases. There's this special material called metal-organic frameworks (MOFs) that's a mix of things from nature and chemicals. It has tiny holes and places that can do special things, and it's being studied a lot for separating gases. Traditional porous materials like activated carbon, silica gel, and molecular sieves have been widely used in industries, which has greatly contributed to industrial growth and people's living standards. MOFs have changeable structures and spots that can do special things. By changing the metal bits or the organic parts, we can control the size of the holes in MOFs, the special spots, and how much surface they have. These things make MOFs useful for storing gases, separating stuff by sticking and making reactions happen in fields like chemistry [1-3]. This paper explores the categories of MOF applications.

Sustainable utilization of magnesium slag through carbonation: a pathway to high-value products with vaterite calcium carbonate

In this study, vaterite - rich materials (VRM) were prepared by carbonating magnesium slag (MS) with the addition of glycine as a regulator and the influence of VRM on the preference of cement was also investigated. The results showed that VRM without glycine exhibited only calcite, whereas the presence of glycine led to an increased vaterite content. The formation of rhombic calcite particles was observed in pure carbonated MS samples, while the addition of glycine during the carbonation process led to the formation of spherical vaterite particles. The compressive strength decreased with increasing MS content, while the high surface area of VRM, nucleation effect of vaterite and the pozzolanic reaction of amorphous silica gel led to an enhancement compressive strength. Overall, the prepared VRM offers a promising approach for transforming solid waste into valuable products through CO2 capture and utilization.

Revolutionary ZVI-Entrapped Sol–Gel Silica Matrices: Efficient Catalytic Reduction of High-Concentration Halo-Organic Compounds—Addressing Bromoacetic Acid Contamination in Industrial Wastewaters

The de-halogenation of highly concentrated halo-organic compounds using Zero Valent Iron entrapped in silica matrices as a catalyst was investigated. This study aimed to evaluate the effectiveness of the Zero Valent Iron-entrapped organically modified silica matrices in transforming highly concentrated hazardous halogenated compounds into environmentally benign materials in the presence of BH4−. The Zero Valent Iron-entrapped silica gel matrices were synthesized using the sol–gel method. The de-halogenation products were analyzed using high-performance liquid chromatography. The results suggest that the Zero Valent Iron-entrapped silica matrices are effective catalysts in the de-halogenation reaction of halo-organics by BH4− with 100% efficiency. The current work also highlights the complete de-bromination of harmful wastewater generated by the bromoacetic acid manufacturing industry using Zero Valent Iron-entrapped silica matrices. Therefore, Zero Valent Iron-entrapped silica matrices can be considered potential candidates for the catalytic removal of highly concentrated halo-organic compounds from contaminated water. This technology can play a crucial role in reducing the environmental impact of hazardous substances.

Effects of relative humidity on carbonation kinetics and strength development of carbonated wollastonite composites containing sodium tripolyphosphate

Assessing the impact of relative humidity (RH) on carbonation kinetics is crucial for the sustainable and high-strength advancement of CO2-activated Ca-bearing materials incorporating phase-controlling additives. This work focuses on the carbonation kinetics, mechanical properties, and microstructure evolution of carbonated wollastonite composites containing sodium tripolyphosphate (STPP) when exposed to various RH levels. Results show that RH plays an important role during the carbonation of wollastonite, functioning both as a reaction material and accelerating role for wollastonite carbonation. The carbonation rate and the phase transition reaction of poorly crystalline CaCO3 is accelerated at RH ranging from 70% to 95%, favouring to cementitious behaviour of CaCO3 and results in denser microstructure, especially for 85% RH. The carbonation reaction is composed of two distinct stages, namely, wollastonite dissolution and precipitation of the stage-1 and ion-diffusion controlling of stage-2. Among them, the addition of STPP prolong the carbonation duration of stage-1. The degree of carbonation (DOC) of the internal layer sample is higher than that of the outermost layer sample. CaCO3 and silica gel are evenly distributed indirectly, which reduces the elastic modulus at 85 % RH. However, regardless of RH, the cementitious efficiency of poorly crystalline CaCO3 is the highest, followed by calcite and silica gel. Consequently, STPP modified carbonated wollastonite shows highest strength when exposed to 85% RH (67.3 MPa at 7 days). Our study provides a unique way toward developing the STPP-containing carbonated wollastonite system for high performance carbonated materials.

Effect of Exchange Dynamics on the NMR Relaxation of Water in Porous Silica.

The interaction of molecules, in particular, water, with solid interfaces has been studied by a multitude of methods, among them nuclear magnetic resonance spin relaxation. The frequency dependence of the relaxation times follows patterns that have been interpreted in terms of the molecular orientation and dynamics. Several different model approaches could successfully explain limiting cases of 1H relaxation dispersion in systems with rigid surfaces such as silica gel or glass, but none of them can reproduce the relaxation of both 1H and 2H nuclei, which differ in their respective relaxation mechanisms, dipolar vs quadrupolar. From detailed studies of the dynamics of hydration of water in biological materials, the importance of hydrogen and molecular exchange to the longitudinal relaxation time of T1 was demonstrated. In this work, exchange times of both H2O and D2O in hydrophilic silica gel are varied in a controlled fashion in a wide range using disodium hydrogen phosphate, and the effect of physical exchange on spin relaxation is quantified for the first time in such systems using the exchange-mediated reorientation model.

A methodology for selection of solid desiccants in energy recovery ventilators

Controlling indoor humidity levels is essential for maintaining acceptable indoor air quality in buildings. The use of energy recovery ventilators (ERVs) is an energy-efficient way to regulate indoor air humidity. Fixed-bed regenerators and rotary wheels are widely used ERVs because of their high sensible and latent effectiveness. These ERVs are made of desiccant-coated substrates, which enable them to transfer moisture between the supply and exhaust air streams. However, the moisture transfer ability of ERVs depends on the physiochemical and sorption properties of desiccants. Extensive, full-scale experiments are required to determine the best desiccant material for these systems. This paper presents a simplified method of selecting suitable desiccant materials for ERVs. The methodology involves important characterization methods, literature correlations for performance prediction, and cost-effective testing methods prior to full-scale testing, and full-scale test methods are discussed in detail. Furthermore, the performance of a few newly derived materials is evaluated and compared with that of conventional desiccants such as silica gel and molecular sieves. The highest latent effectiveness was obtained for composite of super absorbent polymer (SAP) with potassium formate (SAP-HCO2K-50 %), all-polymer porous solid desiccant (APPSD) and metal organic framework (MOF)–MIL–101 (Cr), followed by activated carbon fibre felt (ACF) Silica sol-LiCl30, SAP, silica gel, MOF–303, and molecular sieve. Researchers and manufacturers would benefit from the proposed methodology and presented data in developing new desiccant materials for ERV applications.

Ionogels in Aqueous Media: From Conductometric Probing of the Ionic Liquid Washout to the Design of More Stable Materials

Although the most promising applications of ionogels require their contact with aqueous media, few data are available on the stability of ionogels upon exposure to water. In this paper, a simple, easy-to-setup and precise method is presented, which was developed based on the continuous conductivity measurements of an aqueous phase, to study the washout of imidazolium ionic liquids (IL) from various silica-based ionogels immersed in water. The accuracy of the method was verified using HPLC, its reproducibility was confirmed, and its systematic errors were estimated. The experimental data show the rapid and almost complete (&gt;90% in 5 h) washout of the hydrophilic IL (1-butyl-3-methylimidazolium dicyanamide) from the TMOS-derived silica ionogel. To lower the rate and degree of washout, several approaches were analysed, including decreasing IL content in ionogels, using ionogels in a monolithic form instead of a powder, constructing ionogels by gelation of silica in an ionic liquid, ageing ionogels after sol–gel synthesis and constructing ionogels from both hydrophobic IL and hydrophobic silica. All these approaches inhibited IL washout; the lowest level of washout achieved was ~14% in 24 h. Insights into the ionogels’ structure and composition, using complementary methods (XRD, TGA, FTIR, SEM, NMR and nitrogen adsorption), revealed the washout mechanism, which was shown to be governed by three main processes: the diffusion of (1) IL and (2) water, and (3) IL dissolution in water. Washout was shown to follow pseudo-second-order kinetics, with the kinetic constants being in the range of 0.007–0.154 mol−1·s−1.

CO2 hydrate formation in superabsorbent hydrogels for carbon capture—A comparison of water-confined framework vs non-water framework

This study investigates the kinetics of CO2 hydrate formation in saturated hydrogel particles—water-confined frameworks—through both experimental and numerical methods, and compares the results with those obtained in silica gels, silicon-based frameworks. Three hydrogel materials with varying swelling ratios were synthesized via radical polymerization. An advanced shrinking core model was developed, incorporating factors of CO2 solubility, gas diffusion, gas–water reaction, capillary effects, and hydrogel functional groups. Results showed rapid CO2 hydrate growth within the first 100 min, with CO2 uptake reaching 78%–82% of the final amount by 600 min. The highest percent water conversion achieved was 96.6%. Simulations indicated a significant decrease in CO2 diffusion coefficient through the hydrate shell over time, especially in hydrogels with higher methacrylic acid content. Capillary effects diminished as the reaction proceeded, with final water consumption via capillaries accounting for 14.4%–26.7% of the total. Hydrogels with higher swelling ratios and higher agglomeration degree formed more porous hydrate shells, enhancing CO2 diffusion but resulting in lower overall CO2 uptake due to their lower water content. Comparisons with hydrophilic porous silica gel revealed that, although hydrogels initially posed greater mass transfer resistance, they ultimately exhibited superior CO2 absorption capacity and rate.